1. Field of the Invention
The present invention relates to a laser handpiece which is held by an operator to use for the performance of treatments such as a dental treatment.
2. Description of the Related Art
In the field of dental treatment, for example, a in which root canal preparation in which part of a tooth to be ground. In the root canal preparation, a rotating reamer is inserted into a root canal and a dentin of the root canal wall is ground. The root canal preparation is conducted with, for example, an object for removing any infection which has entered a dental tubule. In the root canal preparation, the dentin of the root canal wall must be removed by a thickness which is constant in a peripheral direction. Usually, a root canal has a section of a nearly long elliptic shape. Therefore, when the dentin is circularly ground by using a reamer, a normal portion of the dentin which is not required to be ground is also ground. In the treatment using a reamer, processes are used such as: (1) anesthetization; (2) opening of the pulp chamber; (3) extirpation of pulp; (4) root canal debridement by using several kinds of reamers; (5) processing of root canal tip end by using a fine reamer; (6) disinfection; (7) drying; and (8) gutta-percha filling. Such process produce problems such as the treatment is difficult to conduct, and the treatment requires a prolonged time period. In such a treatment using a reamer, recently, the treatment itself is greatly advanced by a combination of the treatment and the measurement of a root canal length. However, the fundamental technique, i.e., grinding by using a reamer is not advanced at all. Among dental treatments, particularly, a root canal preparation treatment has unstable factors because it is impossible for an operator perform the treatment while visually inspecting the site to be treated. As a result, the root canal preparation is considered as one of the most difficult treatments.
Under such circumstances, recently, a laser treatment using a laser beam has been developed in the field of dental treatment. In a treatment using a laser beam, a laser handpiece is used which comprises a main body and a laser probe attached to the main body. A laser beam generated by a laser beam source is emitted from an emission end portion of the laser probe. In a treatment using a laser beam, evaporation and sterilization processes by the laser beam irradiation can be conducted on the dentin and soft tissues (including a gingivae, a dental pulp, etc.).
In addition to the dental treatment field, treatments using a laser beam are known in other fields, too. An example of such treatments is a treatment of pollinosis in which the cortex of the nasal cavity is irradiated with a laser beam, such as a CO.sub.2 laser beam, so as to conduct evaporation or coagulation. In such a treatment of pollinosis, if the laser beam irradiation is conducted in a wrong direction, normal tissues are destroyed. Therefore, such a treatment involves a heavy risk depending on the irradiation direction.
An example of a laser probe which is used in such a laser treatment is proposed in Japanese Examined Patent Publication JP-B2 4-54460 (1992). For example, the laser probe is used in an operation of anastomosing blood vessels which were accidentally cut, in a short time period. In such an operation, cut sections of blood vessels are butted against each other, and the butted portions are irradiated with an annular laser beam from the inside of a blood vessel. In order to emit such a laser beam, the emission end portion of the laser probe has a circular conical shape. The laser beam which has been totally reflected by one oblique wall face of the emission end portion is emitted through the other oblique wall face which is at the symmetrical position, thereby allowing the laser beam to be emitted in a ring zonal shape. According to this configuration, the butted portions of the blood vessels can be anastomosed by one irradiation.
Additionally there is known a laser knife which is disclosed, for example, in Japanese Examined Patent Publication JP-B2 61-40419 (1986). In the laser knife, an emission end portion through which a laser beam is emitted is formed into a circular conical shape, and a flat face of a small diameter is formed at the tip end of the emission end portion. Because of the above-mentioned configuration of the emission end portion, a laser beam of the laser knife is concentrically emitted from the tip end face of the emission end portion in the axial direction, and the linearly emitted laser beam is used for evaporation of vital tissues.
The laser probe disclosed in JP-B2 4-54460 has been developed with the object of anastomosis of cut blood vessels. In the laser probe, therefore, a laser beam is emitted only laterally from the emission end portion in a ring-like shape, and the laser beam is not substantially emitted in the forward and axial direction. If a laser beam is emitted from the emission end portion in the forward and axial direction, normal portions other than the butted portions of blood vessels are irradiated with the laser beam, so that the normal portions are adversely affected by the laser beam irradiation. therefore, the laser probe is not intended to emit a laser beam forward from the emission end portion.
In the laser knife disclosed in JP-B2 61-40419, a fiber probe is not used. Therefore, the laser knife cannot be used in a treatment in which a laser knife is to be inserted into a narrow space, such as a dental treatment. In addition, because of the configuration for the use as a laser knife, the laser beam is emitted forward from the emission end portion in the axial direction. Therefore, the laser knife is not intended to emit a laser beam in a ring-like shape in a lateral direction with respect to the emission end portion.
In a dental treatment, for example, a root canal treatment, the dentin of a site facing a narrow space must be evaporated. In the case of root canal preparation, for example, when a laser probe is inserted into a root canal, the emission end portion of the laser probe is directly opposed to the root apex. When a laser beam is emitted laterally from the emission end portion of laser probe in a ring-like shape as disclosed in, for example, JP-B2 4-54460, the dentin of the root canal wall at the root apex, and the dental pulp in the apical dental foramen at the root apex cannot be irradiated with the laser beam. Therefore, the dentin of the root canal wall at the root apex, and the dental pulp in the apical dental foramen cannot be evaporated. When a laser beam is emitted forward from the emission end portion of the laser probe in the axial direction as disclosed in JP-B2 61-40419, the dentin of the root canal wall at the root apex and the dental pulp in the apical dental foramen can be evaporated, but the evaporation cannot be conducted on the whole periphery of the root canal. Under these circumstances, in the field of a dental treatment, it has been eagerly requested to develop a laser handpiece having a fiber probe which enables the dentin of the root canal wall in the range from the root canal orifice to the apical dental foramen to be evaporated as required.